RAMALLAH, West Bank — Mahmoud Abbas got a major boost in his increasingly bellicose showdown with Hamas on Saturday, with a U.S. diplomat saying he expects a crippling embargo to be lifted once the Palestinian president appoints a government without the Islamic militants.

But the money is unlikely to reach Gaza, now controlled by Hamas and cut off from the world.

The new Cabinet is to be sworn in today in the West Bank, where Fatah forces stormed government offices on Saturday, just three days after Hamas seized control of Gaza and Abbas dismantled the Hamas-Fatah coalition government in response.

Abbas issued a decree just after midnight today annulling a law requiring the new government to be approved by parliament, which is dominated by Hamas.

Hamas spokesman Sami Abu Zuhri said the decree was illegal. “This escalates the crisis, and the president bears the responsibility for all the consequences of these developments,” he said.

In another boost for Abbas, Israeli Prime Minister Ehud Olmert said the new Palestinian government would create a “new opportunity” for the peace process. Olmert has long welcomed Abbas as a negotiating partner, but said Abbas’ alliance with Hamas made peacemaking difficult.

“We have a new opportunity … that we haven’t had in a long time,” Olmert told reporters on board his plane shortly before taking off for a meeting at the White House.

“The situation has changed, which enables diplomatic progress. … We intend to act to take advantage of this situation,” he said. “A government that is not Hamas is a partner.”

In Gaza, panicked residents stocked up, fearing growing shortages of food, fuel and other staples as the crossings of the fenced-in strip with Israel and Egypt remained closed. Hundreds of other Gazans rushed to the border crossing with Israel to try to escape Hamas rule, but found gates locked. Israeli troops briefly fired warning shots.

Senior officials of Abbas’ Fatah movement, who had fled Gaza, started reaching the West Bank. The head of Palestine TV said he had crawled for several hundred yards to evade gunfire at the Gaza-Israel crossing before making it to safety.

“Hamas has always targeted me. Once they fired shots at my car. And they wrote on their Web site that I am broadcasting sedition,” Abdel Salam Abu Nada said. Recently, he received an ominous text message on his cell phone saying, “Your punishment is coming.”

Across Gaza, Hamas cemented control. Prime Minister Ismail Haniyeh, who has ignored Abbas’ order firing him, replaced Fatah security commanders with his own men, and Hamas gunmen rounded up their opponents’ weapons. In the southern town of Khan Younis, members of the most powerful local clan refused to hand over their guns, and a firefight erupted. Hamas fighters stormed the homes of clan members, saying they confiscated drugs and a weapons cache.

Two Fatah loyalists were killed Saturday in what Fatah alleged were revenge killings. Also, the bodies of seven Hamas members were found in the basement of the Preventive Security Service headquarters, a Fatah stronghold captured Thursday, and the bullet-riddled corpse of a Fatah field commander turned up in southern Gaza. More than 100 people were killed a week of clashes.

In the West Bank, gunmen from Abbas’ Fatah movement attacked Hamas-run institutions, taking control of the parliament.

and several government ministries. Chanting “Hamas Out,” they planted Fatah and Palestinian flags on rooftops. They attacked Deputy Parliament Speaker Hassan Kreisheh, an independent, and left only after warning that government workers with Hamas ties could not return.

In Gaza, Deputy Parliament Speaker Ahmed Bahar of Hamas called Abbas’ attempt to form an emergency government illegal.

Abbas, meanwhile, angrily rejected attempts by Arab League chief Amr Moussa to mediate between him and Hamas’ supreme leader, Khaled Mashaal. Abbas aide Yasser Abed Rabbo said the president would not engage in a dialogue with “killers.”

In the showdown, much of the international community, including the U.S., the European Union and moderate Arab states, is backing Abbas. Declarations of support were likely to be followed soon by a resumption of foreign aid to the Palestinian Authority.

It is not clear yet whether the international funds would reach Gaza, since it was the Hamas victory in legislative elections that led to the embargo 15 months ago.

The U.S. consul general in Jerusalem, Jacob Walles, met with Abbas at his headquarters in Ramallah on Saturday, and said the embargo is expected to be lifted once the new government is sworn in.

“I expect that we are going to be engaged with this government,” Walles said after the meeting. “I expect that early next week. There will be some announcements in Washington, specifically about our assistance and about the financial regulations.”

The boycott, which has crippled the Palestinian economy, continued even after Fatah joined Hamas in a coalition in March.

Hamas has not explained how it would run Gaza without foreign support or contact with the outside world. Israel controls Gaza’s borders, wielding tremendous influence over the movement of people and goods in and out of the area.

On Saturday, there were signs of panic. One Gaza City baker distributed tickets to those lined up for bread. Sarifa Hadad, a mother of seven, bought $40 worth of food, including tomato paste and shortening, and was going from store to store to buy more. “They say the borders are going to be closed, so we are searching for sugar and supplies,” she said.

Israel will eventually allow basic supplies into Gaza to prevent a humanitarian disaster, said Public Security Minister Avi Dichter. However, he said Israel would consider Gaza a “terrorist entity” and try to cut off its weapons supply. He said this might require an Israeli deployment along Gaza’s border with Egypt, to halt smuggling.

Israel withdrew from Gaza in 2005, ending a 38-year-old military occupation.

Dozens of Gazans, meanwhile, converged on Gaza’s Erez crossing with Israel in hopes of fleeing. One man was carried on top of a luggage trolley with his leg bandaged. Hassan, 21, a presidential guard trainee, said he was shot in the fighting. He gave only his first name because he was afraid of retribution.

About 150 waited at the gate separating Gaza from Israel. Some carried large suitcases, others held tiny plastic bags. One young man shouted “bye, bye, Gaza,” and waved as he walked through the covered walkway that leads to the Israeli side.

Symbols of Fatah control, including the Gaza City residence of the late Yasser Arafat were looted. Abbas’ office said looters took furniture, including a bed, as well as presents the legendary leader had received in four decades at the helm of Palestinian politics. Hamas security forces later arrived and locked the house. Hamas denied anyone had broken into the building.